Generally, an electronic device (e.g., a personal computer (PC) or portable terminal) has an interface for data communication with an external electronic device. As a representative example, an electronic device may have a universal serial bus (USB) terminal and may communicate data with an external electronic device through the USB or a wireless communication module (e.g., a Wi-Fi or Bluetooth). Electronic devices (or external devices) having USB terminals may include host mode-dedicated devices, such as personal computers, device mode-dedicated devices, such as USB memories, and on-the-go devices that operate in one mode of a host mode and a device mode according to connections, such as tablet PCs or smartphones.
USB has been developed to provide an enhanced and easy-to-use interface while allowing users of electronic devices including PCs to connect with peripheral devices positioned away at various distances. USB has been initially developed considering laptop computers and this have made significant contributions to connectors for small peripheral devices. Among others, USB may advantageously reduce a tangle of cables that may have an influence on the installation of a mini computer.
USB has been a selective interface for electronic devices including PCs because it provides a simplified connection to users. USB eliminates the need of other connectors for printers, keyboards, mouses, or other peripheral devices and may support a wide range of data types from slow mouse inputs to digitalized audios and compressed videos.
Today's USB devices communicable with a host computer system on USB include USB printers, scanners, digital cameras, storage devices, and card readers. A USB-based system may request that a USB host controller be present in a host system and that the operating system (OS) of the host system support USB and USB mass storage class devices. USB devices may perform communication at low speed, full speed, high speed, and super speed through USB buses. Connections between a USB device and a host include a power line, a ground line, and two pairs of data lines (TX+, TX−, RX, and RX−). When the USB device is connected to the host, the USB device determines an operation speed using a pull-up resistor on the D+ line. When the USB device operates at full speed, high speed, or super speed, the D+ line (the D− line if the device is a low-speed device) turns up to high. The USB device then removes the pull-up resistor in an electronic manner and continues to communicate at high speed.
The electronic device may connect with an external device (e.g., a PC, smartphone, or USB memory) via USB to communicate data or power. As such, when the electronic device connects with the external device via USB, the electronic device may operate in a host mode (or master mode) or device mode (or slave mode). When two devices are connected via USB, one of the devices operates in the host mode, and the other operates in the device mode. A normal electronic device plays a fixed role in the host mode or device mode depending on its unique characteristics. For example, a PC operates always in the host mode, and a USB memory always in the device mode. A USB connection requires a pair of one host-mode electronic device and one device-mode electronic device. When host-mode electronic devices are connected together or device-mode devices connect together, the USB operation cannot be done normally. In order to prevent wrong connections and to allow the user to make a connection between a pair of host-mode device and device-mode device, the USB specifications distinctively define the USB connector architecture as shown in the following table.
For example, a host-mode device has a standard-A connector, and a device-mode device has a standard-A plug so that the host-mode device and the device-mode device can make a connection therebetween, but a device-mode USB device having a Standard-B connector cannot be coupled with a device-mode USB device having a standard-A plug. The following Table 1 represents the connector-plug matching between USB electronic devices.
TABLE 1Receptacle(Standard or PD)Plugs Accepted (Standard or PD)USB 2.0 Standard-AUSB 2.0 Standard-A or USB 3.1 Standard-AUSB 3.1 Standard-AUSB 3.1 Standard-A or USB 2.0 Standard-AUSB 2.0 Standard-BUSB 2.0 Standard-BUSB 3.1 Standard-BUSB 3.1 Standard-B or USB 2.0 Standard-BUSB 2.0 Micro-BUSB 2.0 Micro-BUSB 3.1 Micro-BUSB 3.1 Micro-B or USB 2.0 Micro-BUSB 2.0 Micro-ABUSB 2.0 Micro-B or USB 2.0 Micro-AUSB 3.1 Micro-ABUSB 3.1 Micro-B, USB 3.1 Micro-A, USB 2.0Micro-B, or USB 2.0 Micro-A
A device that is fixed to operate in the host mode, such as a PC, is designed to have a standard-A connector, and a USB device fixed to operate in the device mode, such as a USB printer, is designed to have a Type-B (Standard-B or micro-B) connector.
However, some electronic device, such as tablet PC or phone, need selectively have the host mode function and device mode function depending on a counterpart device connected thereto. In such case, when the electronic device has a micro-AB connector, it may support both a host mode device having a micro-A plug and a device mode device having a micro-B plug.
The USB specifications define such function as the on-the-go (OTG) mode at which one of the host mode and the device mode may be variable selected depending on the counterpart device connected with the USB device or user scenarios. A USB device supporting the OTG function physically supports the micro-AB connector to allow for equipment of both the micro-B plug of the host mode device and the micro-A plug of the device mode device and electrically has an identifier (ID) signal in the USB connector so that when the ID signal is equal to or less than a certain voltage, it operates in the host mode, and when the ID signal is equal to or greater than the certain voltage, it operates in the device mode. As such, the functions of the USB device may be variable defined. For example, for a portable terminal supporting the OTG function, when the portable device is connected with an electronic device, such as a PC, through a normal cable to which no ID signal is connected, the portable terminal operates in the device mode and is thus recognized merely as a memory, and when the portable terminal is connected with a USB memory via an OTG cable or OTG gender whose IP pin is connected to a ground, it operates as a USB device having a host mode function. The OTG gender is a middle adapter to physically connect a device mode-dedicated USB device to an electronic device supporting both the host mode and the device mode.
When an electronic device of the related art communicates signals with an external device connected via USB, the electronic device communicates signals at the same signal strength in the host mode and device mode, and thus, the USB connection (or recognition or data communication) experiences problems with excessive signal strength.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.